To satisfy the demand for more sophisticated electronic devices, each device chip needs to be smaller in size and have more functions. Not only that, a superior additional value should be provided through a combination of applications based on integration of chips having different functions from one another. In a case where a new application is added to a wireless communication device, for example, forming one chip that includes an analog processing circuit for wireless communications and a digital circuit for signal processing is considered effective. To realize this, various requirements in design specifications are expected to be fulfilled particularly in the field of development of packages for device chips and in the general mounting technology in a later stage.
Particularly, when a high-frequency semiconductor chip or a power semiconductor chip is mounted, there exist a large number of requirements for mounting technology, since the strength of signals to pass is high (several W or higher), frequency is high (several GHz or higher), or electrical impedance matching and an insertion loss reduction are necessary. Therefore, there are many problems with design and processing in forming packages and forming modules in later stages.
Those conventionally used structures are manufactured as modules by inserting individual semiconductor chips into a package material that is a metal, a ceramic material, or a combination of those materials, and mounting the semiconductor chips, together with another element such as a passive component, on a printed board or the like. For example, a high-frequency chip called an MMIC (Monolithic Micro wave Integrated Circuit) needs to achieve both electrical impedance matching at the input/output unit and a reduction in insertion loss of electrical signals. To realize that, a high-frequency chip is die-bonded to a package material formed with a metal, a ceramic material, or a combination of those materials by using a material such as Au or Au(Sn), and is then wire-bonded with an Au wire or the like. The high-frequency chip is hermetically sealed therein, and is completed as one package. Those components are then mounted, together with a capacitor, an inductor, a resistor, and the like, on a printed board by using soldering, wire bonding, and the like. In this manner, a high-frequency module is completed as a system.
The frequencies to be handled in a high-frequency semiconductor chip range over several digits, and various degrees of power pass through such a semiconductor chip. Therefore, it is necessary to select a package and a mounting method suitable for circumstances of use. Also, in a case where semiconductor chips having different functions are formed into one package or module, there is a demand for novel mounting technology that can form a package without a large ceramic package, so as to reduce package sizes and achieve a higher degree of integration.
In a high-frequency device, the existence of frequencies other than the frequency (such as the carrier frequency) to be subjected to signal processing often adversely affects the signal processing. This is due to the existence of frequencies called harmonics (frequencies equal to integral multiples of fundamental). In signal processing based on wireless communication technology, frequencies that are equal to odd multiples of fundamental are particularly expected to be restrained.
Therefore, in designing high-frequency devices, restraints on harmonics are often taken into account from the beginning. For example, an element is formed by combining an open stub, a short stub, an inductor, a capacitor, and the like in a semiconductor chip, so as to restrain harmonics.
However, when those semiconductor chips are mounted on a ceramic package, a printed board, or the like, further generation of harmonics due to parasitic components or the like resulting from the mounting system becomes a problem. In addition to that, in a signal processing circuit using an amplifier, oscillation of frequencies of harmonics might occur.
Therefore, there is a demand for a structure that restrains generation of harmonics due to parasitic components or the like in mounting semiconductor chips.